Is Ammonia the transportation fuel of the future?

Over the last 100 years, petroleum fuels have dominated due to their high energy content, relative ease of storage, and their abundance.  The age of abundant oil is ending, however, and while the new finds seem to be fewer and farther between, the demand for petroleum fuels has only increased.  The coming scarcity is obvious to many, and while some debate how much oil still exists, nearly everyone agrees that we will reach a point when petroleum will no longer be a viable source of fuel.  While there is agreement on the eventual end of petroleum fuels, there has not been any real consensus on what will be the new power source of all transportation.   Many potential alternatives have been proposed, from corn-derived ethanol to hydrogen, but there are prohibitive problems with nearly all of these methods.  One interesting alternative that has not received much attention, is the use of ammonia as a liquid fuel.

Ammonia, which has the chemical composition of NH3, can be combusted with oxygen to produce nitrogen gas and water.  The reaction is exothermic, and while ammonia’s energy content is about half that of gasoline, the fact that its combustion produces only nitrogen gas and water makes it’s use as a fuel increasingly attractive as CO2 regulation becomes more likely.

I attended a symposium on offshore wind in Houston recently, put on by the Ocean Energy Institute, and one of the speakers spoke of the potential to use ammonia as a transportation fuel, and ammonia production as a means of energy storage.   His proposal centers on using off-peak power from massive offshore wind turbines to run water desalinization plants, and then strip the hydrogen from the purified water to combine with nitrogen to create ammonia.  The draw of this proposal is that it will make use of the typically unwanted off-peak power to produce pure water and ammonia, both of which are already in high demand today.

Is this too good to be true?  Well, no, not really, but there are several hurdles that must be overcome before we are driving around in ammonia powered vehicles.  First,  while ammonia production is already over 150 million tones per year, most of that is produced through either natural gas, and it is mostly used for fertilizers.   Since current ammonia production utilizes fossil fuels, using what we have now as a fuel would not really be any ‘greener’, so the first step is developing commercial-scale ammonia plants that require only electricity, water, and N2 (from air) as inputs.  By using only these three inputs, all of which can be theoretically produced by renewable power, then the cycle becomes carbon-free.  I believe this is not nearly as simple as it sounds, but I do think it is well within our capabilities as a society. While the production of ammonia would have to be scaled up by about a factor of 10, the up-side is that we already know and understand how to store and transport ammonia safely and economically.  Ammonia is a gas at room temperature, but it does compress into a liquid at around 125psia, which makes it much more user-friendly than hydrogen gas.  Ammonia can also be combusted in traditional internal combustion engines with only minor modifications required, which is a huge benefit considering there are over 250 million cars in the US alone.

Overall, I believe that without breakthroughs in electrical storage technologies, liquid fuels will remain the best choice for powering transportation vehicles.  The portability, power density, ease of refueling, and ease of storage is what makes gasoline and diesel and other liquid fuels so popular, and why finding a sustainable fuel replacement is so vital.  Is ammonia the fuel of the future?  It is very possible, but only time will tell.

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2 Comments

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2 responses to “Is Ammonia the transportation fuel of the future?

  1. bimalamin

    Before reading this post I never thought that ammonia could be used widespread as a fuel to power our cars and trucks, I thought that the only transportation use was in farm diesel engines, so I found this reading fascinating. I like the idea and think it was an informative post, but just to play devil’s advocate here, I am going to argue against its use (somewhat).

    First and foremost, though it can be stored at a relatively low pressure as a liquid, ammonia is extremely dangerous if exposure occurs, which is very easy if improperly handled. If anhydrous (or without water) ammonia, which is how I assume it will be used, leaks for example during a crash it can be extremely hazardous to anyone around.

    Some of the dangers from exposure are described by a Purdue professor of Agricultural Engineering below, which I found here:
    “Anhydrous ammonia is a strong alkali that can cause painful skin burns. Because of its low boiling point, anhydrous ammonia can burn by freezing as well as by caustic action. Even mild exposure can cause irritation to tissues of the eyes, nose and lungs. Prolonged breathing can cause suffocation. However, the water-absorbing nature of ammonia causes the greatest injury, especially to the eyes. Permanent damage can result.”

    Further though the idea to use offshore wind power at off-peak times to convert salt water into clean water then into ammonia sounds very appealing, but offshore wind power is extremely expensive, and a lot of infrastructure needs to be put in place to bring all that power to shore. Fresh water, as the post Measuring the Water Footprint of the Energy We Consume talks about, is a highly valuable commodity. If we were able to cost effectively produce fresh water through the desalinization process why don’t we do it more now for areas which suffer from drought? Also rather than use the electricity to create clean water, then use more electricity to manufacturer ammonia from that clean water, why not just use the off-peak power to recharge plug-in electric vehicles over night?

    Additionally, NOx is produced when burning ammonia which can be neutralized with an acid neutralizing agent, but now you have the issue of storing and transporting an acid to make sure the ammonia combustion is clean. This creates another set of issues about the environmental impact of production and transportation of a neutralizing agent.

    Finally, we will run into the same problem as we currently have with natural gas powered vehicles, the infrastructure necessary to support retail distribution does not exist. This is a problem but I feel it is somewhat insignificant as our infrastructure will have to be revamped no matter what direction we chose to move with regard to the fuel that will power our future.

    Not sure if the link copied correctly so here it is again:
    http://www.ces.purdue.edu/extmedia/S/S-71.html

  2. johnnylee711

    First, thanks for letting us know that it is possible to use ammonia as a fuel in our vehicles. I have heard of hydrogen, methane, natural gas, and batteries as alternative energy storage options for vehicles but never ammonia.
    I like the idea that ammonia has the potential to be a carbon-free fuel from its production stage all the way to end-use stage as a fuel in an internal combustion engine. However, this means that energy for the production stage and energy for transporting the fuel must come from a renewable resource such as wind, solar, hydro, etc. It is possible, but I bet capacity limits of our current renewable resources would not allow carbon-free ammonia production on a large scale such that it would replace the fuel America uses in its vehicles. There was a comment that argued Nox emissions would result from the combustion process, which would indeed make a good argument for opponents of ammonia fuel. However, Matthew Zipchen claims in his report (1) that, “real world trials have found that ammonia fuel results in 75% less NOx emissions than gasoline, when burned in an internal combustion engine and combined with a catalytic converter, as cars are today.”
    A professor at the Polytechnic University in Brooklyn, Dr. Vito Agosta, is a huge proponent of using ammonia as a fuel in vehicles (2). Agosta claims that there are no huge developmental costs and the price of a ammonia fueled car wouldn’t be significantly increased. In fact, Zipchen talks about a Canadian company called, Hydrofuel Inc, which does ammonia-fuel conversion systems for gasoline engines, which cost between 6 to 8 thousand dollars (1). Agosta also claims that an infrastructure for ammonia fuels already exists (2). Agosta states that, “handling and storage technologies are presently available and can readily be transferred to the general population.” I do agree with the previous commenter that ammonia is a hazardous fuel. However, so is gasoline and diesel. A big challenge for engineers would be to insure ammonia remains safely contained in the event of an automobile collision. This is a similar concern engineers currently face when designing gasoline and diesel tanks.
    While researching ammonia-fueled cars I came across a video (3) of Canadian, Greg Vizina, who converted his 1981 Chevy Impala to run on ammonia. I personally think the video is very cool and highly recommend that you watch it. Politicians during that time were fascinated by the ammonia fueled car and Canada’s energy minister took the car for a drive. Vizina even claims it was cheaper to operate his car on ammonia than on gasoline. What amazed Vizina the most was the fact that hype from politicians quickly died down. Vizina thinks that since the government owned the petroleum company, Canada had no incentive to develop a competing fuel.

    (1) http://www.docstoc.com/docs/24047214/Ammonia-as-Fuel-for-Internal-Combustion-Engines-in-Agriculture
    (2) http://www.memagazine.org/contents/current/webonly/webex710.html
    (3) http://www.gregvezina.com/

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